1. Field of the Invention
The present invention relates to a method of injecting a pulverized fuel into a blast furnace, and more particularly to a method of injecting a pulverized fuel generally regarded as a burning resistant fuel having a low combustibility, from a fuel injection burner to a tuyere of the blast furnace, which method may improve the combustion rate of the burning resistant fuel.
2. Description of the Prior Art
In recent blast furnace operations, injection of a heavy oil as a fuel has been shifted to an all-coke operation, which has proceeded to injection of a fine coal powder. However, pulverized fuel such as fine coal powder or the like (hereinafter referred to generally as "pulverized fuel") has drawbacks in that it has low combustibility as compared with heavy oil, and contains incombustible components such as an ash content. Therefore, various countermeasures against such drawbacks are required in the injecting operation of pulverized fuel.
In the above circumstances, the present applicant has conducted research so as to accomplish an effective method of injecting the pulverized fuel, and has proposed a technique as disclosed in Japanese Patent Publication No. 60-53081 (U.S. Pat. No. 4,490,171), for example. According to this technique, the injection position of the pulverized fuel is located at an optimum distance upstream of a tuyere, so that both the requirements of improvement in the combustion rate of the pulverized fuel and prevention of ash deposition in the blow pipe may be satisfied. This method may prevent such ash deposition on an inner wall of the blow pipe even when the temperature of a hot blast air to be supplied into the blow pipe is increased, thereby meeting both the above-mentioned requirements.
As described in the aforementioned published specification, at page 4, FIG. 5, it is necessary to use a hot blast air having a high temperature of at least 1050.degree. C. for high combustion rate. Accordingly, the operation temperature of a hot blast stove must be increased, which is disadvantageous from the viewpoint of energy savings. Additionally, the life of a refractory formed furnace wall and duct is shortened to reduce maintenance of the equipment.